U.S. patent application Ser. Nos. 11/010,947, 11/010,948, and 11/010,949, all filed on Dec. 13, 2004, and incorporated herein by reference, describe a method of producing conductive and transparent coatings comprising metal nano-powders. The method comprises the steps of (i) admixing metal nano-powder in a solvent with a least one ingredient of the group: binder, surfactant, additive, polymer, buffer, dispersant and/or coupling agent to obtain an homogenized mixture; (ii) admixing the homogenized mixture with water or a water-miscible solvent or a mixture of water-miscible solvents to form a W/O type emulsion; (iii) applying the emulsion to a surface to be coated by various techniques such as screen printing, spreading, spin coating, dipping, etc.; (iv) evaporating the solvent from the emulsion; and (v) sintering the coated layer so a conductive and transparent coating is formed on the surface of the substrate.
In one embodiment of the transparent conductive coatings described in the aforementioned patent applications, the solvent in the homogenized mixture is an organic solvent or mixture of organic solvents having an evaporation rate that is higher than the evaporation rate of water. The resulting coating is in the form of an ordered or random conductive pattern, wherein the pattern is obtained spontaneously or as the result of a printing technique. While the conductivity of these coatings is surprisingly high, it is desirable in some cases to enhance the conductivity to more closely achieve the conductivity of bulk silver without adversely affecting the optical properties of the coating. It is also desirable in some cases to improve the stability of the emulsion prior to coating.